• Steel and Composite Structures
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• v.45 no.6
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• pp.907-929
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• 2022

Compression experiments were conducted to investigate the compressive behavior of built-up open-section columns consisting of four cold-formed steel channels (BOCCFSs) of different lengths, thicknesses, and cross-section sizes (OB90 and OB140). The load-displacement curves, failure modes, and maximum compression strength values were analyzed in detail. The tests showed that the failure modes of the OB90 specimens transformed from a large deformation concentration induced by local buckling to flexural buckling with the increase in the slenderness ratio. The failure modes of all OB140 specimens were deformation concentration, except for one long specimen, whose failure mode was flexural buckling. When the slenderness ratios of the specimens were less than 55, the failure modes were controlled by local buckling. Finite element models were built using ABAQUS software and validated to further analyze the mechanical behavior of the BOCCFSs. A parametric study was conducted and used to explore a wide design space. The numerical analysis results showed that when the screw spacing was between 150 mm and 450 mm, the difference in the maximum compression strength values of the specimens was less than 4%. The applicability and effectiveness of the design methods in Chinese GB50018-2002 and AISI-S100-2016 for calculating the compression strength values of the BOCCFSs were evaluated. The prediction methods based on the assumptions produced predictions of the strength that were between 33% to 10% conservative as compared to the tests and the finite element analysis.

• International conference on construction engineering and project management
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• 2022.06a
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• pp.170-178
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• 2022

A high-performing Earned Value Management System (EVMS) can influence project success and help stakeholders meet project objectives. Although EVMS processes are well-supported by technical guidelines and standards, project managers often face challenges related to the project culture, team, resources, and business practices that make up the project environment within which an EVMS is being used. A comprehensive literature review revealed a lack of a data-driven and consistent assessment frameworks that can gauge the environment surrounding EVMS implementation. This paper will discuss the EVMS environment of construction and environmental projects, and examine its impact on cost performance. The authors used a multi-method approach to identify 27 environment factors that make up the EVMS environment, assessing them on 18 construction and environmental projects worth over $2 billion of total cost. Research methods employed include: (1) a literature review of more than 300 references; (2) a survey of 294 respondents; and (3) remote research charrettes with more than 60 participating expert practitioners. Culture (one of the identified environment categories) was found to be relatively more important in terms of its impact on the EVMS environment, followed by people, practices, and resources. These exploratory results show statistically significant differences in cost performance between completed projects with either a good or poor environment, for the sample projects. Key environment factors are outlined, and guidance is provided to practitioners around how to set up an effective EVMS environment in a construction or environmental project to inform decision-making and support achieving the project cost objectives successfully.

• Journal of the Korean Society for Precision Engineering
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• v.15 no.2
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• pp.154-161
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• 1998

Prototypes of a design are always needed for the purpose of visualization and evaluation in the aspect of manufacturability functionality, and aesthetic appearance. Since the prototyping process requires a significant amount of cost and time, various rapid prototyping processes are recently being introduced in the process. However, it is usually necessary for a part built up by a rapid prototyping system to be refined by a post-processing process, in which the stair steps on the surfaces, the support structures (if they exist), and the unprocessed material are eliminated. This post-processing is usually done manually and is a time-consuming task. Especially, eliminating the trapped volumes, the volume of the unprocessed material entrapped by the solidified portion, is sometimes impossible in some processes. This study provides a designer with a tool to detect the existence and to calculate the quantity of the trapped volumes at the given build-up direction, so that the proper build-up direction is chosen or the part is built by pieces to avoid the problems caused by the trapped volumes in advance. Since the proposed algorithm can efficiently calculate the amount of the trapped volumes at any build-up direction, it has the potential of such application as optimizing the build-up direction to minimize the trapped volumes.

• Journal of Ocean Engineering and Technology
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• v.5 no.1
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• pp.97-105
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• 1991

In this paper, the fatigue strength and the fatigue crack propagation behaviors of the round bar specimens which were spirally built up by welding and subsequently hardened by quenching were investigated. The material used was SF60 which was whdely employed in mechanical components, especially shafts. Fatigue tests were conducted at the fully reversed condition(R=-1) and axial and load control in the room temperature ahd air environment. The experimental results were expressed by both the range of stress intensity factor ($\Delta{K}$) and the effective range of stress intensity factor ($\Delta{K}_{eff}$). It was clarified that applying of quenching after the building up welding process improved the fatigue strength and the gatigue crack propagation property in the low range of $\Delta{K}$ of the built up round bar specimen.

• Proceedings of the Korean Institute Of Construction Engineering and Management
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• autumn
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• pp.230-233
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• 2003

As the consumer's consumption standard has raised, occupants' needs for the apartment is diversified and complicated. But the existing mass housing supply method has many problems and it couldn't satisfy the dwellers' various needs and overall expected life span. In order to correspond those needs, construction firms have introduced several method, such as plus option, minus option, on-time option, change up service and so on. The custom-built apartment is more supplementary and it can reflect the consumer's needs to the apartment directly. But after running the custom-built apartment, several problems is revealed. So. in this study, I defined the general idea of the custom-built apartment and then collect the case of the custom-built apartment.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.04b
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• pp.14-16
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• 2008

Built-in voltage in organic light-emitting diodes was studied using modulated photocurrent technique ambient conditions. From the bias voltage-dependent photocurrent, built-in voltage of the device is determined. The applied bias voltage when the magnitude of modulated photocurrent is zero corresponds to a built-in voltage. Built-in voltage in the device is generated due to a difference of work function of the anode and cathode. A device was made with a structure of anode/$Alq_3$/cathode to study a built-in voltage. ITO was used as an anode, and Al and LiAl were used as a cathode. A layer thickness of Al and LiAl were 100nm. Obtained built-in voltage is about 1.0V in the Al layer was used as a cathode. The obatined built-in voltage is about 1.6V in the LiAl layer was used as a cathode. The result of built-in voltage is dependent of cathode. We can see that the built-in voltage increase up to 0.4V when the LiAl layer was used as the cathode. These results correspond to the work function of LiAl which is lower than that of Al. As a result, the barrier height for an electron injection from the cathode to the organic layer could be lowered when the LiAl was used as a cathode.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2009.05c
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• pp.189-197
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• 2009

• Proceedings of the KWS Conference
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• 2002.05a
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• pp.152-154
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• 2002

• Korean Architects
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• s.480
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• pp.62-69
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• 2009

• Proceedings of the Korean Institute of Interior Design Conference
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• 2006.05a
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• pp.268-271
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• 2006

The purpose of this study was to identify the influence of living factors on TVOC(Total Volatile Organic Compounds) concentrations for newly-built apartments. The field measurements of TVOC concentrations were made totally 30 times(5 times per one subject house) in six apartment units in which residents recently moved. Those apartments authorized its business approval before May 2004, the Act of Indoor Air auality Management for multi-use facilities. The findings were as follows: The TVOC concentrations of the measured subject apartments ranged from about 1/10 of the recommended standard for multi-use facilities($400{\mu}g/m^3$) to up to 90 times as high as the standard. Since then, the Recommended Standard of Indoor Air Quality Management for newly-built apartment house was announced in December 2005. In accordance with this standard($2390{\mu}g/m^3$) it ranged from about 1/100 to up to 15 times as high as the standard. The subject house whose TVOC concentrations reduced below the recommendation standard in the shortest period had the largest amount of ventilation (all the windows were open for ventilation in the past three months) among ail measured houses. The reason of another house whose TVOC concentrations were much higher than the rest was fronted with new furniture in the room. It's recommended that they should open all the windows for at least three months for ventilation in newly-built houses, and it would be better to avoid remodeling than needs be.